Precancerous skin lesions

Actinic keratosis

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• Definition: UV-induced precancerous skin lesion that may progress to skin cancer.
• Epidemiology: occurs especially in individuals with light skin who are over the age of 50
• Etiology: sun exposure (e.g., from working outdoors)
• Clinical features
  • History: Asymptomatic or mild pruritus, burning, or tenderness; history of chronic sun exposure.
  • Physical Exam:
    • Classic appearance: Erythematous, rough, scaly macule or papule.
    • Key tactile sign: “Felt better than seen” (palpable sandpaper-like texture).
    • Size: Typically < 1 cm.
    • Distribution: Sun-exposed areas (face, balding scalp, ears, dorsal hands, forearms, lower lip [actinic cheilitis]).
    • Variant: May develop a prominent keratin projection (cutaneous horn).
• Pathology
  • Parakeratosis: Retention of nuclei in the stratum corneum. t
  • Atypical keratinocytes: Confined to the basal layer of the epidermis (partial thickness dysplasia).
    • Note: If full-thickness dysplasia → Squamous Cell Carcinoma in situ (Bowen disease).
  • Solar elastosis (blue-gray degeneration of collagen) in the dermis.
• Management:
  • Isolated / Few lesions: Cryotherapy (liquid nitrogen) or surgical curettage/shave.
  • Multiple / Field cancerization: Topical 5-Fluorouracil (5-FU) or topical imiquimod (warn pts about expected erythema/crusting); photodynamic therapy (PDT) is second-line.
  • Prevention: Daily broad-spectrum sunscreen (SPF ≥ 30) and sun avoidance.
• Prognosis
  • Lesions may either regress, persist, or progress to cutaneous squamous cell carcinoma (SCC).
  • The degree of epithelial dysplasia determines the risk of cutaneous squamous cell carcinoma.